Local Survey Control NetworksOn-going needs?

John Ritchie| National Geodetic Office

XXV FIG Congress, 16-21 June 2014

• Organisational roles/responsibilities

• Positioning Strategy

• [Changing] role/requirements of local networks

- Geodetic, Cadastral, Other users

• Who else can provide service?

• What are the hurdles?

• Responsibilities: - network maintenance, records,

database management

Presentation will cover

• Land Information New Zealand

(LINZ) is the government

agency that has the

responsibility for administering

the survey system.

• Integrated system providing

- underlying spatial reference

framework (geodetic)

- common and regulated

system for accurate

documentation of property

location (cadastral)

Landonline

• Components of the geodetic and cadastral

systems are integrated in the electronic

Landonline survey and title system

• Lodgement of geodetic and cadastral digital

datasets for validation, authorising and

integration

National control network

• Active stations – PositioNZ, GeoNet,

Private

• Used for datum connections to

international reference frame,

national and regional deformation

monitoring, hazard monitoring

and general positioning

services

National control network

• Passive control – 100K + marks –still

being developed

• Uses include:

- local deformation monitoring, national

height network, local transformation,

cadastral horizontal and vertical

networks, digital cadastre

improvement, basic geospatial

network

Positioning Strategy

Change of focus

• While passive control networks will

continue to be an important component

• There is an increasingly broad range of

users and uses to be considered, and

• A wider range of options available for

delivering positioning products.

Current situation

• Close to completing passive network

But

• Faced with limitations of finite resources required

to cover a broadening range of activities

However

• Still a demand from users and a commitment

from LINZ to provide passive control

Are there other options?

Other options to deliver control

• Active control networks – PositoNZ (LINZ),

GeoNet (GNS Science) & Private/commercial

Provide access to the datum but don’t necessarily

add to passive local network

• May require users to incorporate deformation

models into their calculations

However with

additional services…

Online GNSS processing service

• Removes the requirement for users to directly

address deformation issues to provide

coordinates in terms of the local datum

• Does require a relatively long observing session

And with further developments

To:

• Enable data processed by the online service

to be integrated into the network database,

and

• Provide functionality for users to submit

additional mark details to support the

coordinate data

• This process would support both cadastral

and non cadastral users

0%

10%

20%

30%

40%

50%

60%

70%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014

Percent urban

rural

Cadastral survey datasets

• Increasing use of GNSS,

particularly in rural areas

• Regulatory requirement to

tie into geodetic control

• Current Landonline data

formats limit the usability of

data for integration.

• Current rules only allow

bearings & distances

• Loss of value

Incorporate GNSS vectors into Cadastral Datasets

System would allow cadastral surveys to incorporate

GNSS vector data into their Landonline datasets

Advantages

• Control placed where it is needed

• On a “just in time” basis

• Networks will be developed/maintained for as

long as there is a user requirement

• At a fit for purpose density

• Removes the requirement for users to deal

directly with deformation issues

• Maximises the use of observation data

Issues…….

• Systems need to be in place to ensure required

standards are met

• Do we attribute the source of data?

• More straight forward for Cadastral Surveys as

we have some control and certification.

• How do we bring in and manage other users

And observations

• Need to get systems absolutely right for users to

recognise the benefits and readily adopt.

No or minimal additional overhead

• Previous initiatives have not been

overwhelmingly successful e.g.:

supply GNSS vector data directly to LINZ

Geodetic Office for processing.

• While these processes provide control there is

still the overhead of providing and maintaining

records (database)

Network Maintenance

There are overheads to maintaining local control:

• Maintaining database – Importance of

maintaining current, up to date supporting data

and documents

• Also provides scope for crowd sourcing

Network Maintenance

There are overheads to maintaining local control:

• Mark protection service to ensure marks aren’t

destroyed –marks are constantly under threat

from other activities (e.g. maintenance

of underground utilities)

• Also incorporates aspects

of crowd sourcing

Conclusions and Observations

• Recognised demand for cadastral and other users

and uses

• Required to maintain datum, but in the future

could be replaced by other methods.

• Crowd/industry sourcing is a viable

alternative – will sustain the system

based on user needs

• Collecting data is not the issue –

ensuring systems allow and enable

integration

• Maximising the use of data

Questions?